EarlyReflectionsFast.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "DSP/BufferVectorOperations.h"
#include "DSP/IntegerDelay.h"
#include "DSP/LongDelayAPF.h"
#include "DSP/BufferOnePoleLPF.h"
#include "DSP/FeedbackDelayNetwork.h"
 
namespace Audio
{
    struct FEarlyReflectionsFastSettings
    {
        // Early reflections gain
        float Gain;
 
        // Delay between input signal and early reflections
        float PreDelayMsec;
 
        // Input sample bandwidth before entering early reflections
        float Bandwidth;
 
        // Early reflections decay (lower value is longer)
        float Decay;
 
        // Early reflection high frequency absorption factor
        float Absorption;
 
        SIGNALPROCESSING_API FEarlyReflectionsFastSettings();
 
        SIGNALPROCESSING_API bool operator==(const FEarlyReflectionsFastSettings& Other) const;
 
        SIGNALPROCESSING_API bool operator!=(const FEarlyReflectionsFastSettings& Other) const;
    };
 
    // Basic implementation of early reflections using a predelay, low pass filter and feedback delay network (FDN). The FDN
    // utilizes four delay lines where each delay line consists of an all pass filter and low pass filter to control diffusion
    // and absorption.
    class FEarlyReflectionsFast
    {
    public:
        
        // Limits for settings
        static SIGNALPROCESSING_API const float MaxGain;
        static SIGNALPROCESSING_API const float MinGain;
        static SIGNALPROCESSING_API const float MaxPreDelay;
        static SIGNALPROCESSING_API const float MinPreDelay;
        static SIGNALPROCESSING_API const float MaxBandwidth;
        static SIGNALPROCESSING_API const float MinBandwidth;
        static SIGNALPROCESSING_API const float MaxDecay;
        static SIGNALPROCESSING_API const float MinDecay;
        static SIGNALPROCESSING_API const float MaxAbsorption;
        static SIGNALPROCESSING_API const float MinAbsorption;
        
        static SIGNALPROCESSING_API const FEarlyReflectionsFastSettings DefaultSettings;
        
        // InMaxNumInternalBufferSamples sets the maximum possible samples in an internal buffer.
        SIGNALPROCESSING_API FEarlyReflectionsFast(float InSampleRate, int32 InMaxNumInternalBufferSamples, const FEarlyReflectionsFastSettings& InSettings=DefaultSettings);
        SIGNALPROCESSING_API ~FEarlyReflectionsFast();
 
        // Sets the reverb settings, clamps, applies, and updates
        SIGNALPROCESSING_API void SetSettings(const FEarlyReflectionsFastSettings& InSettings);
 
        // Process the single audio frame
        SIGNALPROCESSING_API void ProcessAudio(const FAlignedFloatBuffer& InSamples, const int32 InNumChannels, FAlignedFloatBuffer& OutLeftSamples, FAlignedFloatBuffer& OutRightSamples);
 
        // Silence internal audio.
        SIGNALPROCESSING_API void FlushAudio();
 
        // Clamps settings to acceptable values. 
        static SIGNALPROCESSING_API void ClampSettings(FEarlyReflectionsFastSettings& InOutSettings);
 
    private:
        void ApplySettings();
 
        FEarlyReflectionsFastSettings Settings;
        float SampleRate;
 
        FAlignedFloatBuffer LeftInputBuffer;
        FAlignedFloatBuffer LeftWorkBufferA;
        FAlignedFloatBuffer LeftWorkBufferB;
        FAlignedFloatBuffer RightInputBuffer;
        FAlignedFloatBuffer RightWorkBufferA;
        FAlignedFloatBuffer RightWorkBufferB;
 
        FFDNCoefficients LeftCoefficients;
        FFDNCoefficients RightCoefficients;
 
        FFeedbackDelayNetwork LeftFDN;
        FFeedbackDelayNetwork RightFDN;
 
        FIntegerDelay LeftPreDelay;
        FIntegerDelay RightPreDelay;
 
        FBufferOnePoleLPF LeftInputLPF;
        FBufferOnePoleLPF RightInputLPF;
    };
}